I smoked a whole chicken Beer can style low and slow @ 225 once, and only once. It tasted like a wet cigarette. So don't make that mistake, or make the mistake, and you'll never do it again. Stay higher around 350, and you'll be just fine. I'm a beer can chicken kinda guy, but I've never spatchcocked a chicken, so I can't comment.
Joe. UDS, mUDS, Deluxe Traeger, Infrared Grill; Maverick ET-732, iQue 110, RT600C Thermapen